DESCRIPTION: Among the herbicides and pesticides, 2,4-D is the most commonly used broadleaf herbicide. Many studies have demonstrated an increased risk of certain cancers among agricultural workers. While the mortality from cancer is increased among farmers, the overall mortality of farmers is less than the general population. This apparent paradox can be reconciled if one hypothesizes that herbicides have a selective effect on some, but not all, aspects of the immune system. The hypothesis of this project is that 2,4-D increases the incidence of immunologically related cancers by inhibiting NK cell activity either directly or by altering the profile of cytokines secreted from a type 1 (interferon-gamma) to a type 2 (IL-4) pattern.